The present invention relates to electrical discharge machines (EDM) and, more specifically, to a wire guiding device for use in electrical discharge machines whereby wire of relatively small diameters used by the electrical discharge machines may be more readily and easily threaded through the wire guiding device.
EDM machines using a wire electrode are presently commonly used for making precise cuts on various materials such as metals and cutting the metal or workpiece to a given desired shape or configuration. The wire is drawn through two wire guides and the workpiece is situated between the two guides. The wire and workpiece are placed at different electrical potentials and a controlled electric spark traveling from the wire to the workpiece causes the workpiece to be eroded and cut in a predetermined desired shape or configuration.
The guides through which the wire travels are connected to arms that selectively situate the wire in position for cutting the desired shapes. Furthermore, the guides often are located within an assembly including a preguide, a pickup for placing an electrical potential on the wire and various gaps for receiving deionized water or a liquid for cooling the guide assembly and flushing the workpiece.
When threading the wire through the guide assembly, such as, for example, if the wire were to break during operation, the operator must either disassemble the wire guiding assembly and thread the wire therethrough or attempt to thread the wire while the assembly is intact. As can be appreciated, disassembling the wire guide assembly is extremely burdensome, time consuming, and undesirable. Accordingly, the preferred method is to attempt to thread the wire by pushing the same through the wire guide assembly. However, this threading process is also quite often burdensome and time consuming because the wire quite often becomes caught within the various components of the wire guide assembly and the wire is not easily threaded therethrough. This is especially true when the wire must travel, for example, through a preguide and thereafter an off center electrical pickup and then, finally, through a precise guide hole such as, for example, in a diamond. This threading process is further laborious when the wire must, at the end, be threaded through a diamond hole approximately only 0.0002 inch greater in diameter than the wire itself. Further yet, as the wire is decreased in diameter size, for example, less than 0.004 inch, the longitudinal stiffness of the wire over the distance that it must be threaded is significantly reduced. The small diameter wire, in fact, has a tendency to curl and is realistically and practically impossible to thread through the final diamond wire guide hole after it has been pushed through the preguide and the off center electrical pickup. This problem is further enhanced in view of the fact that thin or small diameter wire has a greater tendency to break during operation and, thus, a long threading operation means substantially more down time of the electrical discharge machine translating to inefficiency and greater production costs.